There is a well-known technology for changing the frequency at which a host vehicle transmits information through vehicle-to-vehicle communication. For example, a technology disclosed in Patent Literature 1 decreases the frequency at which a host vehicle transmits information using a wireless communication apparatus via vehicle-to-vehicle communication when receiving a precautionary target vehicle ID from a different vehicle through vehicle-to-vehicle communication and the received precautionary target vehicle ID is not equal to the vehicle ID of the host vehicle. Herein, the precautionary target vehicle ID indicates a vehicle to which the different vehicle should pay attention to.
When the wireless communication apparatus of the host vehicle decreases the information transmission frequency for transmitting the information through the vehicle-to-vehicle communication, the amount of electrical power consumed by the information transmission will be reduced and the power consumption of the wireless communication apparatus will be reduced. However, in the wireless communication apparatus, the power consumption in standby state for waiting to receive information is greater than the power consumption for information transmission. This is because, information may be sent from external device at any time, and the wireless communication apparatus needs to get prepared for the information sent from external device at any time. Thus, the technology disclosed in Patent Literature 1 may fail to substantially reduce the power consumption of the wireless communication apparatus.